Ever been to a big city before?
Drag queens, flashers, 12-year old whores, 80 year old thugs, business men, hippies, drunks, and so many other things are known to be "common" in places like New York City (which Gotham is very heavily depicted as). Seeing some greasy-haired fucker with face paint on is nothing special. No one is gonna look twice at him, because they have the big city "I've seen it all" mentality.